1. Field of the Invention
The present invention relates generally to the closure of intravascular defects and more specifically to a device for closing a septal defect, the device being delivered to the site of the defect by a catheter and comprising a metallic or polymeric material which is adjusted by mechanical means to a configuration which functions as a plug.
2. General Background
The heart is divided into four chambers, the two upper being the left and right atria and the two lower being the left and right ventricles. The atria are separated from each other by a muscular wall, the interatrial septum, and the ventricles by the interventricular septum.
Either congenitally or by acquisition, abnormal openings, holes or shunts can occur between the chambers of the heart or the great vessels (interatrial and interventricular septal defects or patent ductus arteriosus and aorthico-pulmonary window respectively), causing shunting of blood through the opening. The ductus arteriosus is the prenatal canal between the pulmonary artery and the aortic arch which normally closes soon after birth. The deformity is usually congenital, resulting from a failure of completion of the formation of the septum, or wall, between the two sides during fetal life when the heart forms from a folded tube into a four-chambered, two unit system.
These deformities can carry significant sequelae. For example, with an atrial septal defect, blood is shunted from the left atrium of the heart to the right, producing an over-load of the right heart. In addition to left-to-right shunts such as occur in patent ductus arteriosus from the aorta to the pulmonary artery, the left side of the heart has to work harder because some of the blood which it pumps will recirculate through the lungs instead of going out to the rest of the body. The ill effects of these lesions usually cause added strain on the heart with ultimate failure if not corrected.
Previous extracardiac (outside the heart) or intracardiac septal defects have required relatively extensive surgical techniques for correction. To date the most common method of closing intracardiac shunts, such as atrial-septal defects and ventricular-septal defects, entails the relatively drastic technique of open-heart surgery, requiring opening the chest or sternum and diverting the blood from the heart with the use of a cardiopulmonary bypass. The heart is then opened, the defect is sewn shut by direct suturing with or without a patch of synthetic material (usually of Dacron, teflon, silk, nylon or pericardium), and then the heart is closed. The patient is then taken off the cardiopulmonary bypass machine, and then the chest is closed.
In place of direct suturing, closures of interauricular septal defects by means of a mechanical prosthesis have been disclosed.
U.S. Pat. No. 3,874,388 to King et al. relates to a shunt defect closure system including a pair of opposed umbrella-like elements locked together in a face to face relationship and delivered by means of a catheter, whereby a defect is closed. U.S. Pat. No. 5,350,399 to Erlebacher et al. relates to a percutaneous arterial puncture seal device also including a pair of opposed umbrella-like elements and an insertion tool.
U.S. Pat. No. 4,710,192 to Liotta et al. relates to a vaulted diaphragm for occlusion in a descending thoracic aorta.
U.S. Pat. No. 5,108,420 to Marks relates to an aperture occlusion device consisting of a wire having an elongated configuration for delivery to the aperture, and a preprogrammed configuration including occlusion forming wire segments on each side of the aperture.
U.S. Pat. No. 4,007,743 to Blake relates to an opening mechanism for umbrella-like intravascular shunt defect closure device having foldable flat ring sections which extend between pivotable struts when the device is expanded and fold between the struts when the device is collapsed.
U.S. Pat. No. 4,699,611 to Bowden relates to a biliary stent having radially protruding lobes.
There still exists a need, however, for a simple mechanical method of closing septal defects, either temporarily or permanently, with an improved plug having a unitary construction that is adjusted by mechanical means from a delivery configuration to a configuration which functions as a plug at the site of a defect.